Braking system



March 28, 1939. T, A, BANN|NG J 2,152,917

BRAKING SYSTEM Filed Nov. 11, 1936 3 Sheets-Sheet 1 ATTOR N EY INVENTORgym (-1. Banning Mafia 2, 193, T. A. BANNING, JR,

BRAKING SYSTEM 3 Sheets-Shet 2 Filed Nov. 11, 1936 INVENTOR. Thomasbannm, Jr.

ATTORNEY.

March 28, 1939. T. A. BANNING, JR 2,152,017

BRAKING SYSTEM Filed Nov. 11, 1956 3 Sheets-Sheet 3 Invenror'THOFYIQSAIBCLIIHIYEJR Atty.

Patented Mar. 28; 1939 Thomas A. Banning, Jr., Chicago, 111., assignorto Bendix Products Corporation, South Bend, Ind., acorporation ofIndiana v Application November 11, I936, Serial No. 110,252

15 Claims. (01'. 188-142) J This invention concerns itself withimprovements in braking systems and the like. The features hereindisclosed are intended, and have been designed, especially for use inconnection with 5 so-called trailers which are attached to-anddrawn-along the road by automotive vehicles, but it will presentlyappear that certain of said features may be used in connection withothervehicles; and for this and 'other reasons I do not inlo tend tolimit myself-in this respect, except as I may do so in the claims tofollow. I may also mention in this connection that the present featureshave been especially designed for use in connection with so-calledhouse-trailers" as dis- 18 tinguished from commercial trailers, but donot intend to limit myself in this'respect other than as limited by theclaims. The main object of the invention is to provide an arrangement ofbraking system which shall 20 be completely seli -contained'within thetrailer itself, so that it is'unnecessary to establish any specialconnections between the braking system and devices 01 the automobile ortractor unit to which the trailer is connected, and the trailer asbraking system. In other words, this'ieature of the invention relates'to theprovision of a trailer braking system which will respondautomatically when the automobile or tractor unit is braked,-

and without special connections between the two units for this purpose.The desirability of such an arrangementwill be better understood, whenit is remembered thatthe trailer unit is generally built and soldentirely distinct from the automobile unit, and further, when it isremembered that.

35 a given trailer unit may be attached to any one of many types andsizes of automobile units, and that interchangeability isvery greatly-tobe desired. That is, it is desirable to be able to buy the trailer unitindependently of the automobile 40 unit, and make connection betweenthem thereafter; and in making such connection to be able to secureproper operation of the'trailer braking system without having toestablish special connections to the braking system of the automobile.

45 By this means it will be possible. to effect great saving in the costof initial construction of both units, and also to eliminate the specialwork incident to making connections to the automobile braking system.

50 In connection with the foregoing it is a further object to providefor quick response of the trailer braking system to the varyingrequirements imposed by varying applications of the automobile brakingsystem, both as to amount or degree of 5'5 the-braking force, and theconditions of travel times ineffective.

under which same is created. In this connection itis an object toincrease or decrease the braking effect of the trailerbrakessynchrcnously with corresponding changes of the braking effort ofthe automobile itself. Generally speaking, the '5 application of thetrailer brakes is eifected by an over-riding of the trailer-towards theautomobile. In this connection, as the braking efiect of the automobileis increased with increase of over-riding, the braking eflect of thetrailer brakes is also increased, and vice versa.

A further, object of the invention is to make provision for locking outthe trailer brake system when the automobile is reversed in direction oftravel, so that the trailer brakes will not interfere withsuch reversalof travel. In this connectioh it is a further object to effect suchlockout operation automatically, and without the need of any specialconnection between the automobile and the trailer braking systems, orother devices. v Also, to make provision for resumption of the normalbraking action of the trailer unit system when forward movement is againresumed. Specifically, this result is accomplished, in the arrangementherein disclosed, by a speed governor arrangement whereby the trailerbraking system is at Thus normal backward force exerted on the tractionor draw bar connection from the automobile to the trailer will notactuate the trailer brakes: but the trailer braking sys- 3o hour, orwhen the trailer-is being driven rearwardly at a somewhat higher speed.Inasmuch as reversing movements of an automobile and trailer combinationare generally made only for parking or similar purposes, and alwaysunder great caution, low speeds are seldom, it ever, ex ceeded duringreversing of such a combination.

Specifically, the arrangement herein disclosed 40 is one in which thecontrolling of the operative or inoperative condition of the trailerbrake mechanism is effected by pressure generated-by a small centrifugalpump driven at a speed proportional to the speed of trailer travel. Suchpump is eflected to build up pressure in either direction of rotationand, therefore, for either forward or reverse travel of the trailer; butdue to the form of the vanes of the pump impeller, it is less emcientfor building up such pressure when rotated in a reverse direction thanwhen driven forwardly.

As a consequence this arrangement is such that the necessary speed oftravel of the trailer in a forward direction to build up sufiicientpressure to actuate the lock-out device is less that the necesu.

sary speed of. travel in a reverse direction to actuate-the lock outdevice. Therefore, one-feature of the invention relates to anarrangement in which the trailer may be moved in a backwarddirectionwith its braldng system, rendered in-' effective faster thanthe speed in a forward direction which would render its braking systemineffective, thus making it possible to perform backward movements atspeeds greater than would otherwise be "possible and withoutinterference due to any actuation of the trailer brakes during suchbackwardmovements.

A further feature of the invention relates to the provision of means forequalizing or adjusting'the braking actions exerted on the two trailerwheels automatically with any tendency of the trailer to sway' sidewiseduring travel on the road with the brakes applied. Bince'the forwardpressure of the trailer against the automobile is effected with apivoting effect along the center line or axis of the combination,itfollows that any effect which swings the trailer out of line withrespect to the automobile, during the braklng operation, tends to causeside sway with an accentuated effect; and may become a source of greatdanger on the road. The present featureof this invention relates to anarrangement whereby any such tendency of the trailer to-swing sidewisecausesa momentary or temporary adjustment of the braking actions on thetwo trailer wheels, in such a manner as to tend to draw the trailerautomatically back into alignment with the automobile This result iseffected, in the present disclosure, by means of a momentum or pendulumdevice. operative under the sidewise forces thus to be compensated for.

It win sometimes -be desirable .to-make rovision for locking the trailerbrakes in the "on" condition, even when the traileris standing idle, asfor example, when parked, or when standing on a hill. I'have thereforealso made provision for such locking of'the trailer brakes under suchconditions, and irrespective of the condition of the brakes oftheautomobile or tractor unit.

All or combinations of the results heretofore enumerated may be securedin systems embodying the features of the present invention, and.therefore in-some cases certain of the devices hereinafter to bedescribed may be eliminated 'without detriment to the proper andemcient.

functioning of the remaining devices.

Generally speaking itmay be further stated that it is an object of theinvention to so arrange the trailer braking system that the trailer with7 its braking system is a completely self-contained unit, readyfor'functioning and travel, and may be connected to the automobile ortractor unit in simple manner, and without having to give considerationto the braking systems of either 60 unit and still, when the trailer hasbeen so connected to the automobileunih and the combination is taken outon the road for travel, the trailer braking system will functionperfectly, and in full accord with the braking and retarding actions ofthe'automobile unit.

Specifically, I have also illustrated, andshall describe'the features ofthe present invention as embodied within a hydraulic braking arrange- 70ment, but it will presently appear that certain of said features arealso susceptible of use in connection with mechanical braking systems.

' Other objects and uses of the invention will appear from a detaileddescription of the same,

1 which consists in the features of construction T'igurel;

Figure 3 shows a front end view corresponding Figure 4 shows across-section through atypical form ofequalizer valves, the operatingmech- 15 'anism, therefor being shown diagrammatically and one operatingposition thereof being-shown. in dotted lines; a

- Figures 5, Band 7 showthree consecutive positions, in cross-section,of a typical form of cut 20 out valve; e

Figure 8 shows a cross-section through a typical form of valve in themain line between the "master" cylinder and the brake" cylinders,vto'

reduce or prevent any tendency to hunt" or 25 surge when the automobileor tractor unit is ti-axed";

., Figure 9 liows diagrammatically a layout of simple form in which theside-sway' eliminator arrangement andalso the manual brake lock, 30;

have been eliminated; I

Figure 10 shows diagrammatically a layout of simple form in which the"look-out, for backing. up, and also the "manual brake lock, have beeneliminated; and I Figure 11 shows diagrammatically a layout of simpleform in which the side-sway" eliminator arrangement has been eliminated.v v r Referring first to Figures 1, land 3, I have therein shown thefront end portion of the 40 trailer by the numeral 20. It is shown ashaving the lower frame members 2| and 22, of channel cross-section, thefront ends of which members are brought together to embrace a tubularmember 23, to which the frame members are secured.

The rear end ofthis tubular member is provided with the foot 24 which issecured directly to the front end of the trailer body. iThere is a drawmember 25 telescopically entered into the tubular 1 member 28 so thatsaid draw member may move back and forth to a sufficient-extent toproperly actuate the braking system of the trailer, as will soon beexplained. The front end of this draw member carries theiflxture 26 offamiliar form which may be connected to the companion draw member 21which is in turn connected to the. automobile ortractor unit. A spring18 is placed between the inner end of the draw member II and the foot24, and tends to hold and restore the draw member in the forwardlyprojected condition, but said spring is not heavy enough to prevent-thedraw member from moving back and forth to effect brake actuations' ofthe braking system of the trailer unit.

-A typical. form of master cylinder unit of a hydraulic braking systemis mmmted under theforwardly projecting portions of the frame members 2|and 22. This includes the "master cylinder 29, and the "compensatingchamber ll above the same, and the master plunger it work-' ing in themaster cylinder. The details of these parts require no explanation here,beyond the statement that when the master plunger is moved to itsforward position it permits replen ishment of the oil in the mastercylinder behind forced back it delivers oil under proportional pressureto-the brake cylinders of the two wheel brakes oi the trailer unit.There is a yoke 32 secured to the draw member 25, and a' suitableconplun8- The two wheels of the trailer are indicated-at to thesewheels, and the brake bands"- and 3'! are shown for these brake drums.There are alsoshown the brake wheel hydraulic cylinders 38 individuallines 4| and 42. leading to wheel cylinders.

' connection 45 therefrom; and the casing of this valve has the port-48leading to the vmaster'cylinder,.the port "leading to the'wheelcylinders,

and the port 43 leading back to the compensating chamber 30. This-valveis provided with the control arm 49 which is connected to the restoring'spring 50 (shown as a compression spring in Figure 1). There. is acontrol diaphragm device it which when energized by oil under prestionoil from the master cylinder will be delivered sure will force the arm49 upwards againstthe force of the spring 50, to thereby move the valve.to the position shown in Figure '5. In that posito the wheel cylindersin normal manner for '1 braking functions. When" the pressure within thedevice'5l falls below a certain predetermined ,amount, corresponding toa certain speed of "travel,. the spring ill will overcome the. diahragmpressure and the valve-will be forced .towardsthe closed position ofFigure "I, wherein all of the ports are sealed, including the master Q5.Dllring such closing movement, how-' ever, the valvejwill pass throughthe position de- I picted in Figure 6, wherein the wheel cylinders aretemporarily connected to the compensating chamber; so as to allow theaccumulated pressure lwlthln the wheel cylinders to be released, and Iin'g position of Figure 7 is reached. When the 'positionoi Figure! isfinally reached the master cylinder is'sealed, so that the force exertedon thereby release the wheel brakes before the sealthe master plunger bythe draw member 25, as during backing, is properly resisted.

. The diaphragm device it is actuated to. open the valve to the positionoi Figure 5 when the speed of the trailer exceeds, for example, three orfour miles per hour, or some other relatively low speed. Such speed isso low that the use of the trailer brakesji's no longer necessary toensure complete deceleration of the combined automobile and trailercombination. Whenever the trailer is travelling at a speed greater thansuch minimum speed the valve 43 is in the condition depicted in Figure 5wherein a deceleration of the automobile will ensure application ofthetrailer brakes, and such condition will continue until the speed fallsbelow such minimum speed.. whereupon the valve 43 will shift to theposition .oi Figure 7, passingthrough that of Figure 6; and-whilepassing the position of Figure 6 the accumulated pressure within thebrake cylinders will be released, so that when the trailer finallyfunctioning under travel.

valves inunison and harmony.

comes to rest the brakes will be in released '00 dition, making itpossible to'thereafter push the trailer backwards if so desired. whenthe automobile is subsequently driven forward the. do-

a vice Btwill function as soon as the minimum 5 nection 33 connects saidyoke with the plunger of I the master, cylinder. Consequently, as thedraw member moves back and forththe master er is correspondinglyactuated.

speed is exceeded, to thereby again move the valve 43 into condition forproper'trailer brake It is now seen that I have provided an arrange- Ime'nt such that the functioning of the brake of lo the trailer will notocpur during reversal, but

these brakesgwill be left in released condition at 4 In'the arrangementshown in the drawings I.

: have provided a small centrifugal pump 52,

driven in convenient manner by one of trailer '.wheels', as by the belt53 passing over thepulle'y 54' on the axle of the wheel 34. Thiscentrifugal pump connects by the line 55' to the diaphragm device 5|..sothat'as the trailer speed rises the pressure delivered to the diaphragmdevice rises to the actuating point. Any other convenient means might-besubstituted for operating'the valve 6! in the desired manner.

I have already referred to. the fact that the 5 centrifugal pumparrangement is one in which the actuating pressure for actuating thediaphragm device BI and valve 43 will be developed .by the centrifugalpump at a lower speed oftrail- I er travel forwardly thanthe trailerspeed necessary to. develop suchpressure when travelling backwardly.- I,therefore, contemplate as being is less than a certain predeterminedamount, and v including such devices which will ensure such lock-outaction ,at a greater speed when reversing .thetrailer'than when the sameis travelling for-' wardly. v,

There are the valves 58 and, 51 located in the branch pipes 4| andj42respectively leading tothe wheel brake cylinders. These valves are-ofthe general form shown in Figure 4. They nor- 'mally stand in positionto permit free flow of oil back and forth to the respective wheel brakecyl-' inders: but when said valves are shifted they will allow drainage0! oil from their respective wheel brake cylinders back to the.compensating chamber of the master cylinder. For this p'urpose there areprovided the lines 51. and 58 lead-'- ing from" the return ports of therespective valves to a common line. leading to the compensating chamber.I

There is a pendulum" or momentum device 5 6t pivoted at the point 6! sothat it may-swing back and forth laterallyoi the line of travel of thetrailer. Springs 62 and 63 act on thispendulum at the two sides thereof,and can befad justed by the set screws 64 and 85. Normally thearrangement is such that the pendulum stands in the. central positionshown. This pendulum connects by the links 88 and .61 with the valves.56 and 57 respectivelmso that as the pendulum sways back :and forth'itwill actuate the two. 65'

The arrangemerit iunctions as follows; Assuming that the trailer istravelling uniformly without side sway, oth valves are open,

so that upon application of braking pressure both 7 wheel brakecylinders willbe equally energized. In case-the trailer should sway tothe 'leit'in Figure 2, for example, thependulum would tend to initsoriginal line of traveL' holding. back, and thus aoting'in elfect toturn both of the valves 56 and 51 counter-clockwise, as shown by thedotted lines in Figure 4. In so doing the passage 68 of the right handvalve would be moved to close against the master cylinder and place thebrake wheel cylinder into connection with the line 58 leading back tothe compensating chamber, thereby releasing pressure fromsuch wheelbrake cylinder; but in the meantime, the passage 68 of the left handvalve 55 would remain unconnected with the return passage 51, andtherefore pressure would not be released in the left hand wheel brakecylinder. The result would be that the left hand wheel would continue tobe braked, but the braking action on the right hand wheel would bereleased, either partially or fully; and the left hand wheel wouldtherefore hold back with the greater force, tending to pull the trailerback towards the right, and thereby resist such leftward side sway. Asimilar action would be created in case of tendency to sway to theright. I have thus provided means for automatically compensating forside sway, and for tending to keep the trailer travelling centrallyduring braking actions. It will be noted that this compensating actionis only produced during braking action, but at such time the tendency toproduce side sway is greatest and most dangerous.

In some cases it might be desirable to be able to set the brakes on thetrailer manually, and maintain them in such set condition even when thetrailer has come to complete rest. This might be desirable, for examplewhen the trailer has been parked. I have therefore provided the oilpressure chamber 69 to which the delivery side of the pump 52 isconnected by the line 10, a check valve 1| being placed in such line sothat oil can flow from the pump to the pressure chamher only when thepump pressure exceeds that of the chamber 69, and so that pressure inthe chamber 69 will not be lost when the pump speed falls. A line 12leads from the pressure line 10 to a manual valve 13, which is a threeway valve. From this valve 13 a line 14 leads to the main line 40 sothat pressure may be applied to such main line by opening the manualvalve; and a return line 15 leads from this manual valve to the returnreservoir 16. By this arrangement, when the manual valve is turned tothe brake-on position pressure will be delivered to the wheel brakecylinders, and when the manual valve is turned to the releasing positionthe pressure will be released from the wheel brake cylinders; and

. at another position the line H is sealed so thatthe draw connectioncan properly function to actuate the trailer braking system.

It will be noted that when the automobile or other tractor unit istravelling normally without braking action, the draw connection 25 isextended by the spring 28. Upon the application of braking force to theautomobile brakes, with deceleration of the automobile, the trailer willtend to overrun the automobile, and the draw connection 25 will beforced back. This will cause application of braking pressure to thetrailer brakes, and thereupon the compressing force on the drawconnection 25 will be reduced, with corresponding reduction of thebraking action of the trailer brakes. This will somewhat re;- duce theholding back of the trailer, so that its tendency to again overrun theautomobile will rise; and thus there may be a tendency to build up ahunting action between the automobile and thetrailer. This action ortendency may be accentuated by any irregularities of the braking actionof the automobile due to irregular braking oi. the driver thereof. Inorder to reduce the tendency towards such "hunting I have placed -thevalve device 11 in the main line III. This valve device includes theflap valve 18 normally closing in the direction of the delivery oi! oilto the wheel brake cylinders, and freely opening in the direction ofreturn of oil towards the master cylinder; and this flap valve isprovided with the smaller opening or port 79 which permits flow of oilto the wheel brake cylinders, but under such restriction as will dampenany tendency towards such hunting as just above referred to.

In view of the fact that the centrifugal pump will draw oil into itsintake opening, I have connected the same with the return chamber 16 bythe line 80. In order to limit the back and forth movements of the drawmember or connection, I have provided the pin and slot arrangementbetween the member 25 and the sleeve or tubular member 23, as shown inFiguresl and 2.

It will be noted that in Figures 1, 2 and 3 I have shown all of thefunctions" and devices combined together into a complete system, capableof functioning and performing in all of the manners herein set forth. Inorder to simplify an understanding of the several possible functions andfeatures, and to emphasize that each feature may be used without theother, I have, in Figures 9, 10 and 11, separated these features fromeach other, so that the operation of each one of them may be betterunderstood individually. These several figures will be readilyunderstood without detailed description, and they have been numberedaccording to the numbering heretofore recited in connection with Figures1 to 8 inclusive.

While I have herein shown and described only a single embodiment of thefeatures of my present invention, still I do not intend to limit myselfthereto, except as I may do so in the claims.

I claim:

1. The combination with an automobile tractor unit having the usualbraking system and controls therefor, of a. trailer unit in conjunctiontherewith, wheel brakes on the trailer unit, a yieldable tractorconnection between said tractor unit and said trailer unit yieldablelongitudinally of the combination, brake operating mechanism on thetrailer unit effective to operate the brakes of said unit according tothe condition of yield of said tractor connection, and means normallyrendering inoperative said brake operating mechanism and serving torender the same operative when the speed of the trailer unit relative tothe road exceeds a predetermined minimum amount which minimum amount isindependent of the tractor speed, substantially as described.

2. The combination with an automobile tractor unit having the usualbraking system and controls therefor, of a trailer unit in conjunctiontherewith, wheel brakes on the trailer unit, a yieldable tractorconnection between said tractor unit and said trailer unit yieldablelongitudinally of the combination, brake operating mechanism on thetrailer unit effective to operate the brakes of said unit according tothe condition of yield of said tractor connection, and a speed governoron the trailer unit in connection with the brake operating mechanismthereof effective to render the said brake operating mechanismineffective when the speed of the trailer unit is less than apredetermined amount, substantially as described.

3. The combination with an automobile tractor eluding means ,efiectivetolock out the trailer a r 2,102,017- unit having the usual brakingsystem and controls therefor, of a trailer unit in conjunctiontherewith, wheel brakes on the trailer unit, a yieldabletractor-connection between said tractor unit and said trailer unityieldable longitudinally of the combination, trailer brake operatingmeans, means to actuate-said trailer brake operating means whenthe'yieldable tractor connection is ating -means for saidtrailer-brakes, and means local tothe trailer unit in conjun'ction withthe brake operating means 01 said unit effective} to control theIunctioningof said trailer brake op-' erating means according totendency of the'trailer unit to over-ride the tractor unit. togetherwith means to render said trailer. brake operating means ineffectivewhen the speedof the trailer is less thana predetermined amountirrespectiveoisuch' tendency to over-ride and irrespective of thetractor speed, substantially as described;

5. The combination with an automobile tractor:

. unit having the usual braking system and controls therefor, of atrailer unit in conjunction therewith, wheel brakes on the trailer-unit,brake operating means for said trailer brakes ..and means wholly localtothe trailer unit in conlunction with the brake operating means of saidunit effective to control the functioning ofsaid trailer brake operatingmeans according to" tendency of. the trailer unit to over-ride thetractorunit, and inbrake' operating means when the speed of thecombination is less than a certain predetermined amount irrespective of"such tendency 'tooverride and irrespective of tractor speed,- andthereby render the trailer brakes-inefl'ective at such 1 times,substantially as described.

y 6. The combination with an automobiletractor unit having the usualbraking system and controls therefor, of a trailer unit in conjunctiontherewith,'-wheel brakes onthe trailer unit, brake operating means forsaid trailer brakes means to I ensure operation of the trailerbrakeswhen the tractor unit is being braked, together with means .inconjunction with the trailer brake operating means effective to vary thebraking action on the wheels of the trailer. according to lateral,movements of the'traller, substantially as described.

'7. The combination with an automobile tractor unit having the usualbraking system and contrcls therefor, of a trailer unit in conjunction.therewith,v wheel brakes on the trailer unit, brake operating means forsaid trailer brakes, means to i ensure operation-of the trailer brakeswhen. the

tracto'r'unit isbeing braked, a pendulum device mounted on the trailerfor lateral movement with respect to the direction of trailer travel,and operating. connections between said pendulum device and the, trailerbrake operating means efl'ective to reduce braking action on the side ofthe trailer from which the trailer moves during side sway, substantiallyas described.

8. The combination with an automobile tractor unit having-thusualbraking system and conas described;

trols therefor, of atrailer conjunction therewith, wheel brakes on thetrailer unit, brake operating means for said trailerbrakes, means toensure operation of the trailer brakes when the tractor unit is beingbraked, means to cause diiierential action of-the braking action on thedifferent trailer wheels, and means to control said difierential actionmeans by side sway of the trailer, effectively to reduce the brakingaction of the trailer wheel brake atthe side 0! the'trailer from whichthe sway movementis taking place,

' substantially as described. 1

an automobile tractor i 9 The combination with unit having the usualbraking system controls therefor, of a trailer unit in conjunctiontherewith, wheel brakes for the trailer unit,

brake operating means for said trailer brakes, means to ensure operationof the trailer brakes when the tractor is being braked, and a swaycompensating device on the trailer unit, including a pendulum mounted onthe trailer unit and adapted to swing laterally thereof with lateralside of the trailer from which the trailer is sway ing, substantially asdescribed.

10. The combinationwith an automobile tractor-unit having the usualbraking system and.

controls therefor, of a trailer unit in conjunction therewith, wheelbrakes for the trailer unit, brake operating means for the trailerbrakes, means to ensure operation of the trailer brakes underpredetermined conditions, a pivotal traction connection between thetractor unit and the trailer unit,

permitting lateral sway of the trailer unit with' sway of the trailerunit-,and connections between said pendulum and the trailer brakeoperating "means eiiective to reduce-braking action on the respect tothetractor unit, togetherwith means on the trailer unit to ensuredifferential braking action of the trailer brakes a the two sides 0! thetrailer with reduction of braking action at the side from which thetrailer is swa substantially i 11. The combination with an automobiletractor unit having'a braking system and the usual controls therefor, ofa trailer unit in conjunction wtherewith, wheel brakes for the trailerunit, brake operating means for the trailer brakes, .means to ensureoperation of the trailer brakes under predetermined conditions, apivotal. traction connection between the tractor unit and the trailermeans on the trailer unit to ensure diiferential braking'action of thetrailer brakes at thetwo sides. of the trailer giving a maximumbrakingaction at the side towardswhich the'trailer is swaying,substantially as described.

12. The combination with an automobile,trac-' tor unit having a brakingsystem and-the usual controls therefonfof a'trailer unit in conjunctiontherewith, wheel brakes for the trailer unit, brake operating meansfor'the trailer brakes, and meansto ensure diflerential braking actionat the two sides oi. the trailer operative according to side sway df,thetrailer to ensure a maximum braking action at the side ofthe. trailertowards which the'traller is swaying-substantially as described.

13. The combination with an-automobile traction therewith, a yieldabletraction connection between-the tractor. unit and the trailer unityieldable in the direction of travel of the units,

hydraulic braking means i'orthe wheels of the trailer unit, including amaster hydraulic cylintor unit having the usual braking system and,

controls thereforfof a trailer unit in conjunc- 7 1 unit, permittinglateral sway of the trailer unit v with respect to the tractor unit,together with der and hydraulic wheel brake cylinders, a masterhydraulic line connecting the master hydraulic cylinder with thehydraulic brake cylinders, and a damping valve in said line permittingfree flow of liquid between the master cylinder and the brake cylinderin one direction and restricted flow thereof in the other direction,substantially as described.

14. The combination with an automobile tractor unit having the usualbraking system and controls therefor, of a trailer unit in conjunctiontherewith, a yieldable traction connection between the tractor unit andthe trailer unit yieldable in the direction of travel of the units,hydraulic braking means for the wheels of the trailer unit, including amaster hydraulic cylinder and hydraulic wheel brake cylinders, a masterhydraulic line connecting the master hydraulic cylinder with thehydraulic brake cylinders, together with means for damping hydraulicflow through said line in one direction of hydraulic travel with agreater effect than in the other direction of hydraulic travel,substantially as described.

15. The combination with an automobile tractor unit having the usualbraking system and controls therefor, of a trailer unit in conjunctiontherewith, a yieldable traction connection between the tractor unit andthe trailer unit yieldable in the direction of travel of the units,braking means on the trailer unit, connections between the yieldabletractor connection and said braking means effective to ensure actuationof the trailer braking means under certain conditions of yield of thetractor connection, and means for damping 4 the effectiveness of saidlast-named connections efiectively to create a lag in the braking actionof the trailer unit with respect to the variations of the yieldabletractor connection, substantially as described.

THOMAS A. BANNING, Ja.

